From the moment of his regarding me not as an apprentice, but merely as a curious spectator, who drew and wrote about subterranean vegetable affairs, but had no wish to carry to market my bagful of these glories of the Christmas goose, the excellent man lent himself generously to my designs.
It was agreed between us that the dog should act according to his own instincts, receiving the customary reward, after each discovery, no matter what its size, of a crust of bread the size of a finger-nail.
Every spot scratched by his paw should be excavated, and the object indicated was to be extracted without reference to its marketable value.
In no case was the experience of the master to intervene in order to divert the dog from a spot where the general aspect of things indicated that no commercial results need be expected, for I was more concerned with the miserable specimens unfit for the market than with the choice specimens, though of course the latter were welcomed.
Thus conducted, this subterranean botanising was extremely fruitful.
With that perspicacious nose of his the dog obtained for me both large and small, fresh and putrid, odorous and inodorous, fragrant and offensive.

I was amazed at my collection, which comprised the greater number of the hypogenous fungi of the neighbourhood.
What a variety of structure, and above all of odour, the primordial quality in this question of scent! There were some that had no appreciable scent beyond a vague fungoid flavour, more or less common to all.

Others smelt of turnips, of sour cabbage; some were fetid, sufficiently so to make the house of the collector noisome.

Only the true truffle possessed the aroma dear to epicures.

If odour, as we understand it, is the dog's only guide, how does he manage to follow that guide amidst all these totally different odours?
Is he warned of the contents of the subsoil by a general emanation, by that fungoid effluvium common to all the species?
Thus a somewhat embarrassing question arises.
I paid special attention to the ordinary toadstools and mushrooms, which announced their near advent by cracking the surface of the soil.